Force scroll event inside scrollViewDidEndScrollingAnimation and scro…

…llTo

Summary:
Changelog: [internal]

`onScroll` event needs to be fired when scroll view ends the scrolling animation and when scrollTo is called.
This is how Paper does it and client code might depend on it.

Reviewed By: JoshuaGross

Differential Revision: D24527189

fbshipit-source-id: bdec099f16b3d8c97686975a1f769db4d2c0d832

React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm

@@ -392,6 +392,7 @@ - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
 - (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
 {
   [self _forceDispatchNextScrollEvent];
+  [self scrollViewDidScroll:scrollView];
 
   if (!_eventEmitter) {
     return;
@@ -458,6 +459,8 @@ - (void)scrollTo:(double)x y:(double)y animated:(BOOL)animated
             _scrollView.contentSize.height - _scrollView.bounds.size.height + _scrollView.contentInset.bottom +
                 fmax(_scrollView.contentInset.top, 0),
             0.01)); // Make width and height greater than 0
+
+    [self _forceDispatchNextScrollEvent];
     if (!CGRectContainsPoint(maxRect, offset)) {
       CGFloat localX = fmax(offset.x, CGRectGetMinX(maxRect));
       localX = fmin(localX, CGRectGetMaxX(maxRect));